Conventionally, vehicle speed control devices are known that are provided in a vehicle whose vehicle body moves due to a wheel rotatably attached to the vehicle body rotating as a result of a person manually pushing the vehicle body, and that are capable of controlling the vehicle speed (e.g., see Patent Documents 1 and 2). Patent Documents 1 and 2 disclose speed control devices that are provided in a vehicle configured as a walking supporter or a walking assistance vehicle.
The speed control device disclosed in Patent Document 1 includes a governor brake mechanism section provided within a brake drum with a wheel. The governor brake mechanism section is provided as a mechanism that enables a braking action using a centrifugal force that acts under a rotation speed condition of an output shaft in the brake drum. More specifically, the governor brake mechanism section includes a governor plate that is integrated with the output shaft, a pair of brake shoes having a governor weight structure that are pivotably attached to the governor plate, and a governor spring. The governor spring is attached between ends of the brake shoes and the governor plate. Thus, when the rotation speed of the output shaft is larger than or equal to a predetermined rotation speed, the brake shoes that pivot due to the centrifugal force are pressed against the brake drum, and a braking force is generated.
The speed control device disclosed in Patent Document 2 includes a cylindrical locking disk, a support plate installed within the cylindrical locking disk, a pair of locking pieces, and a spring. The support plate is fixed to a rotary shaft of a wheel, and the pair of locking pieces are pivotably attached to the support plate. The spring connects the pair of locking pieces such that tips of the locking pieces pull each other. Since the pair of locking pieces are pulled by each other with the spring, they do not prevent the rotation of the rotary shaft as long as the rotary shaft rotates at a normal rotation speed. On the other hand, if the rotary shaft rotates rapidly, the support plate also rotates rapidly, and the locking pieces protrude out due to the centrifugal force. As a result, a locking portion of each locking piece is locked at a stepped locking portion formed in the inner face of a circumferential wall of the cylindrical locking disk, and the rotary shaft stops together with the support plate.